Technical Field
The present invention generally relates to methods and systems for photoacoustic tomography. More particularly, the present disclosure is related to photoacoustic tomography using orbital angular momentum (OAM).
Description of the Related Art
Biological and medical imaging technology has been implemented to spatially localize, diagnose, and treat human diseases in a clinical setting. However, most existing biomedical imaging technologies are anatomical, and do not have the capacity to molecularly interrogate a tissue, such as indicating whether a tissue is cancerous or whether the tissue is responding to a particular therapy treatment.
Common imaging technologies include magnetic resonance imaging (MRI), x-ray computed tomography (CT), ultrasonography (US), single photon emission computed tomography (SPECT), and positron emission tomography (PET). These common imaging technologies, however, are still in the pre-clinical phase of experimentation based on the physical characteristics. For instance, MRI technology does not display functional information and has a very high cost, although it provides strong anatomical contrast between soft tissues. CT technology makes use of harmful ionizing radiation, which causes the frequency of use to be limited. In addition, the images produced by CT technology differentiate very little among varying soft tissues. Another imaging technology is ultrasound technology, however, traveling acoustic waves implemented by ultrasound technology are impeded by abrupt changes in density of, for example, bone and/or air, and contrast suffers greatly among soft tissues because the variations in density are relatively minor. Moreover, some imaging technologies, including OCT and US, are strongly affected by speckle interference, which is displayed as random intensity patterns produced by the interferences of a set of wavefronts (e.g., waves having the same frequency, but having different phases and amplitudes). As the reflecting surface is not perfect, an abundance of waves with different phases are generated.
Common optical imaging techniques include diffuse optical tomography (DOT), optical coherence tomography (OCT), angular domain imaging (ADI), fluorescence imaging, and near infrared spectroscopy (NIS). However, these imaging technologies and/or techniques suffer from poor spatial resolution, which is associated with the high scatter of photons in human tissue. Consequently, current biological and medical imaging technologies cannot provide high resolution features, such as absorption contrast, structural imaging, and/or molecular imaging in biological tissues.